The “Casper” project being worked on by the Ethereum development team is simply a fix for a flawed Proof of Stake (POS) system.

As it stands POS has a major flaw to where if a malicious blockchain is formed anyone can profit off of it essential making cryptocurrency useless in this state and is also known as the “Nothing at Stake” problem, where no matter what you do you can’t lose which is good for those people, but bad for the future of crypto-kind so it can’t happen.

The Casper Project(s) being worked on fix this issue by penalizing members of malicious blockchains, in doing so, also cripples the new verifiers where as they get a rejected share that may not be malicious, will lose their stake.